feat: add alot

lib/services/product_service.dart

@@ -2,16 +2,16 @@ import 'package:drift/drift.dart';
 import 'package:uuid/uuid.dart';
 
 import '../database/app_database.dart';
+import '../database/stock_queries.dart';
 import '../models/product.dart';
 
-class InsufficientStockException implements Exception {
-  const InsufficientStockException();
-
-  @override
-  String toString() => 'Not enough stock';
-}
+export '../database/stock_queries.dart'
+    show InsufficientStockException, ProductNotFoundException;
 
 abstract class ProductService {
+  /// Active products, re-emitted whenever the products table changes.
+  Stream<List<Product>> watchProducts();
+
   Future<List<Product>> getProducts();
 
   Future<Product?> getProductById(String id);
@@ -53,15 +53,20 @@ class DriftProductService implements ProductService {
     );
   }
 
-  @override
-  Future<List<Product>> getProducts() async {
-    final query = database.select(database.products)
+  SimpleSelectStatement<$ProductsTable, ProductRow> _activeProductsQuery() {
+    return database.select(database.products)
       ..where((product) => product.active.equals(true))
       ..orderBy([(product) => OrderingTerm.asc(product.name)]);
+  }
 
-    final rows = await query.get();
+  @override
+  Stream<List<Product>> watchProducts() {
+    return _activeProductsQuery().map(_mapRowToProduct).watch();
+  }
 
-    return rows.map(_mapRowToProduct).toList();
+  @override
+  Future<List<Product>> getProducts() {
+    return _activeProductsQuery().map(_mapRowToProduct).get();
   }
 
   @override
@@ -129,49 +134,12 @@ class DriftProductService implements ProductService {
   }
 
   @override
-  Future<void> decreaseStock(String productId, int amount) async {
-    _validateStockAmount(amount);
-
-    final updatedRows = await database.customUpdate(
-      'UPDATE products '
-      'SET stock_quantity = stock_quantity - ? '
-      'WHERE id = ? AND stock_quantity >= ?',
-      variables: [
-        Variable.withInt(amount),
-        Variable.withString(productId),
-        Variable.withInt(amount),
-      ],
-      updates: {database.products},
-    );
-
-    if (updatedRows == 1) return;
-
-    final product = await getProductById(productId);
-    if (product == null) throw Exception('Product not found');
-
-    throw const InsufficientStockException();
+  Future<void> decreaseStock(String productId, int amount) {
+    return database.decreaseStock(productId, amount);
   }
 
   @override
-  Future<void> increaseStock(String productId, int amount) async {
-    _validateStockAmount(amount);
-
-    final updatedRows = await database.customUpdate(
-      'UPDATE products '
-      'SET stock_quantity = stock_quantity + ? '
-      'WHERE id = ?',
-      variables: [Variable.withInt(amount), Variable.withString(productId)],
-      updates: {database.products},
-    );
-
-    if (updatedRows == 1) return;
-
-    throw Exception('Product not found');
-  }
-
-  void _validateStockAmount(int amount) {
-    if (amount <= 0) {
-      throw ArgumentError.value(amount, 'amount', 'Must be greater than zero');
-    }
+  Future<void> increaseStock(String productId, int amount) {
+    return database.increaseStock(productId, amount);
   }
 }